As it becomes more and more common for wireless communication devices to implement multiple wireless access technologies, wireless network operators are beginning to deploy different wireless access networks, also referred to in the art as radio access networks (RANs), which share a same core network. For example, some operators of networks that implement one or more 3rd Generation Partnership Project (3GPP) standards, such as Long Term Evolution (LTE) networks, are planning to integrate WiFi networks into their existing cellular network infrastructure. Such WiFi networks are termed in the standards as “trusted” WiFi networks.
One of the key motivations for 3GPP operators to deploy trusted WiFi networks is to offer operator-hosted Internet Protocol (IP) services and, most notably, IP Multimedia Core Network Subsystem (IMS) voice services over WiFi access, i.e., voice-over-WiFi. To efficiently support voice-over-WiFi, it is important to support handover of voice sessions or calls from the WiFi access network to the cellular access network. For this purpose, the architecture specified by 3GPP for trusted WiFi integration supports “IP address preservation” between WiFi and cellular access networks. IP address preservation enables the wireless communication devices, referred to as user equipment (UE) in the 3GPP standards, to maintain the same IP address when switching an active communication session, such as a voice call, between the WiFi and cellular access networks.
However, simply maintaining the same IP address is insufficient to provide the voice handover performance expected by some users. More particularly, a voice interruption or break that results from the access network change should also be minimized. This is very challenging for UEs that have wireless transceiver equipment that can communicate over both WiFi and cellular access networks but not simultaneously. The voice interruption, for example, for such UEs during handover of an active voice call from the WiFi access network to the cellular access network can oftentimes be greater than ten seconds.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.